316/A4 Stainless Metric Fender Washers

316 Stainless Steel (A4) DIN 9021 Metric Fender Washers

When you need to spread load, protect surfaces, and keep fasteners from pulling through, DIN 9021 fender washers are the correct solution. Our DIN 9021 washers are manufactured from A4 grade 316 stainless steel, providing exceptional corrosion resistance and long term durability in marine, coastal, and industrial environments.

DIN 9021 washers feature a large outside diameter with a precision sized center hole, allowing the load of a bolt or screw to be distributed over a much wider surface area. This prevents damage to wood, fiberglass, aluminum, plastics, and composite materials while also increasing the holding strength of the fastener.

These washers are commonly used anywhere material pull-through, vibration, or surface damage is a concern, including:

• Marine hardware and deck fittings
• Boatbuilding and refits
• Dock and marina construction
• Sheet metal and aluminum assemblies
• Fiberglass and composite structures
• Wood joinery and carpentry
• Industrial and mechanical installations

Unlike standard flat washers, DIN 9021 fender washers provide a much larger bearing surface, making them ideal for thin materials, soft substrates, and slotted or oversized holes.

Why DIN 9021 Matters

DIN 9021 defines the outside diameter, inside diameter, thickness, and flatness of the washer so that it delivers consistent load distribution and proper fit. These are not oversized hardware store washers. They are precision metric components designed to match metric fasteners correctly.

When used in structural or marine applications, having the correct outside diameter and thickness ensures the washer does not dish, deform, or concentrate load at the bolt head.

Material: A4 / 316 Stainless Steel

These washers are made from A4 stainless steel, also known as 316, the industry standard for saltwater and corrosive environments.

• Outstanding resistance to rust and pitting
• Highly resistant to salt, chlorides, and harsh weather
• Excellent strength and toughness
• Non-magnetic in most conditions

This is the same alloy used in marine rigging, through-hull fittings, and offshore hardware, and it significantly outperforms A2, 18-8, and 304 stainless when exposed to moisture and salt air.